Among display device driver circuits, data driver circuits (also referred to as “source drivers”) include driver circuits each for driving a data line of a display panel (LCD (Liquid Crystal Display) panel, an EL (Electro Luminescence) panel, or the like) in parallel, corresponding to data lines for each line, for example. The data driver circuit inputs a digital video signal from a host device such as a CPU, for example, converts the digital video signal to a gray-scale voltage/current corresponding to the digital video signal, and drives the data line of the display panel by the gray-scale voltage/current. The output terminals of the driver circuit are provided corresponding to the data line terminals (terminal electrodes) of the display panel. On the other hand, in scan line driver circuits (also referred to as “gate drivers”), an output of the scan line driver circuit is connected to a gate line of the display panel, and the scan line driver circuit sequentially drives the gate line for a selected line at a high electric potential responsive to a synchronization control signal and a clock signal.
In recent years, the display device driver circuits tend to increase their outputs (or the number of data lines per line and the number of lines on a screen tend to increase), so that the chip size of ICs for driving the display devices (the data driver and the gate driver; hereinafter referred to as “driver ICs”) and the area of a film for mounting the driver ICs thereon (or the number of sprocket holes) tend to increase.
As conventional display devices, there are employed a configuration in which driver IC chips are directly mounted on a glass substrate or the like (COG; Chip On Glass) and a configuration in which the IC chips are mounted on a film substrate (COF; Chip On Film) and interconnect electrodes of the film substrate are connected to corresponding interconnect electrodes of the glass substrate (data line and gate line electrodes). In either case of the COG and the COF, a plurality of output terminals of each driver IC is provided, corresponding to the positions in which the data or gate lines of the display panel to which the output terminals are connected are disposed.
FIG. 5 is a diagram showing an example of a configuration in which a semi-slim type driver IC is mounted on the film substrate. As a publication that discloses a configuration similar to that in FIG. 5, Patent Document 1, for example, is referred to. This Patent Document 1 describes that regarding electrodes for output terminals in a lower row of the driver IC mounted on a glass substrate, wiring need to be routed around from the driver-IC mounting portion to a corresponding output pad. Then, it is described that, due to the reason described above, the area of the glass substrate is increased, so that reduction of the size and weight of the liquid crystal display device cannot be achieved. FIG. 5 is the diagram showing an example in which a technical matter described in conjunction with a conventional art described in Patent Document 1 has been applied to the COF. In the following description, upper and lower and left and right such as in upper and lower sides and left and right sides will refer to the upper and lower and the left and right in appended drawings (plan views).
As shown in FIG. 5, in a semi-slim type driver IC chip 20A, output terminals 21 on the driver IC chip 20A are disposed on a plurality of sides. On the upper side of the driver IC chip 20A, first to ith output terminals are disposed in order on the left side of a region in which a plurality of input terminals 22 are arranged. (Referring to FIG. 5, numerals appended to the sides of the terminals on the IC chip 20A indicate the numbers of the output terminals.) On the upper side of the driver IC chip 20A, (i+1)th, (i+2)th, . . . (j−2)th, (j−1)th, and jth output terminals (in which the appended numerals for the upper and lower sides are serially numbered) are disposed in order from the left to the right. Further, on the lower side of the driver IC chip 20A, (j+1)th, (j+2)th, . . . , (n−1)th, and nth output terminals are disposed in order from the right to the left on the right side of the region in which the input terminals are arranged.
The first output terminal on the lower side of the driver IC chip 20A is connected to a corresponding output pad through wiring 141, while the nth output terminal on the lower side is connected to a corresponding output pad 12 through wiring 14n. Likewise, the kth output terminal on the upper and lower sides of the IC chip 20A (in which k is an integer from 2 through n−1) is connected to a kth output pad 12 through corresponding wiring 14k. As a result, the n output terminals from the first, second, . . . (i−1)th, ith, jth, (j+1)th, and (n−1)th to the nth output terminal are connected in an order in which output pads 12 are arranged (in an order in which data lines or gate lines for connection are arranged). Incidentally, referring to FIG. 5, each of the output pads 12 and input pads 13 is not individually separated for illustration, but is shown as a box specifying an entire region, for simplicity (which also holds true for other drawings).
In the configuration shown in FIG. 5, a wiring routing region 17 for the output terminals on the longer side facing input pads 13 is required. In other words, it is necessary to provide a spacing 16 between the lower side of the input chip 20A and the wiring 141 that is routed in an outermost direction. This spacing 16 is set to such a dimension just enough for routing wirings connected to i (from the first to the ith) output terminals and (n−j) (from the (j+1)th to the nth) output terminals on the left and right sides of the region in which the input terminals 22 are arranged on the lower side of the IC chip 20A to the output pads 12.
In the semi-slim type driver IC chip 20A, the output terminals are disposed on a plurality of chip sides of the semi-slim type driver IC chip 20A in an order of data lines to which the output terminals are connected, so that the size of the chip can be reduced more than in a slim type (refer to FIG. 6 that will be hereinafter described). However, in case the driver IC chip is mounted on a film substrate 10, the wiring routing region 17 becomes necessary. The reason why the wiring routing region 17 becomes necessary is that the film has a single-layer interconnection structure.
Then, in the case of the configuration shown in FIG. 5, the area of the film substrate 10 on which the chip is mounted is increased due to the presence of the wiring routing region 17, so that the number of sprockets 11 (the number of perforations) per film substrate is increased. This means reduction of the number of products manufactured per one film roll, which leads to an increase in the cost of the products.
On the other hand, in the case of the film substrate, there is no advantage in adopting a multi-layer interconnection structure. Further, when the film substrate is configured as a multi-layer substrate, an increase in the cost is brought about. For this reason, the single-layer interconnection having one interconnection layer on the film surface is widely used.
As described above, in the semi-slim type, the wiring routing region 17 becomes larger with an increase in the outputs of the driver IC. The larger the number of the output terminals on the lower side of the IC, the spacing 16 becomes larger. Thus, the number of the sprockets 11 per film substrate (the lengths of the film on both sides) is increased.
FIG. 6 is a diagram showing a configuration in which a conventional slim-type driver IC chip 20B has been employed. As shown in FIG. 6, in the slim-type driver IC, the output terminals are disposed on one side of the chip in the order of signal outputs (corresponding to the data lines or the gate lines to which the output terminals are connected). N driver circuits from one to n, drive the first to nth data lines (gate lines) from the left to the right of the display panel, respectively and the first to the nth output terminals on the IC chip 20B are disposed in order from the left to the right. In FIG. 6, the input terminals 22 are disposed in the whole range of the lower side. The input terminals, however, may be dummy terminals.
As shown in FIG. 6, the number of the sprockets 11 (the number of the perforations) per film substrate is set to five, which is smaller than that of the example shown in FIG. 5 (six). The number of the terminals on the upper side of the IC chip 20B, however, is increased more than that in the semi-slim type in FIG. 5. In other words, in the case of the slim-type chip, the area of the film can be reduced more than that in the semi-slim type. However, the chip size of the driver IC is increased.
Further, in the case of the slim-type chip, the number of needless spaces is increased on an input side (the side for inputting a digital video signal and a control signal). For this reason, reduction of the cost becomes difficult.
Further, in the case of the slim-type chip, the output terminals on the chip are all disposed on one side. Thus, design latitude of the chip (for circuit design and layout) is also constrained, so that design optimization becomes difficult.
[Patent Document 1]
JP Patent Kokai Publication No. JP-A-6-110071 (FIG. 5)